Simple question: How do I estimate an AE model using the umxACE function?
Yes, you can estimate an "AE" umxACE model!
This is done via umxModify and labels - the labels umx applies to every matrix cell/parameter in the model.
in twin models, these labels take the form matrix name + "_" + "r" + row-number + "c" + col-number. So the link from the first latent variable to the second measured variable in the c matrix is labeled c_r2c1.
Just run umxACE to get your saturated model, then drop the c parameters using umxModify
There is an example of this in ?umxACE
This is a powerful tool. You can provide a single label to update. e.g. update = "c_r1c1", this can be a list of labels.
By default they are set to zero, but you can set them to anything via values. By default they are fixed, but you can free variables with free = T.
update = "c_r1c1"
free = T
You can even use regular expressions: umxModify(m1, regex = "c_r.c.”) which would drop all free parameters from the c matrix (as long as there are fewer than 10 rows and columns), which is what you want to create an AE model!
umxModify(m1, regex = "c_r.c.”)
then umxCompare to compare them
Because I am lazy, you can update the model , rename it, and do the comparison all in 1 line!
m2 = umxModify(m1, regex = "c_r.c.”, name = "AE", comp= TRUE)
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